The present invention relates to an SSR (Secondary Surveillance Radar) station for acquiring aircraft information of an aircraft in flight and an aircraft secondary surveillance network.
As is well known, an aircraft in airborne is obliged to send out a desired SSR reply via a transponder when it receives an SSR interrogation from each of SSR stations located in many places. For example, as shown in FIG. 4, such an SSR station sends out its own SSR interrogation to an aircraft 1 with determined interrogation timing and acquires aircraft information such as a position of the aircraft 1 upon receipt of its own SSR reply from the aircraft 1.
Such SSR stations are located in many places. If one SSR station sends out an SSR interrogation to the aircraft 1 and the other SSR station in each of the places acquires aircraft information, a phenomenon called fruit occurs in which the former SSR station receives the other SSR reply which is issued from the aircraft 1 in response to the SSR interrogation of the latter SSR station.
A conventional SSR station has therefore a so-called defruiter function of eliminating fruit and adopts a method of eliminating an undesired other SSR reply. In other words, as shown in FIG. 5, the defruiter function is fulfilled so as to eliminate the other reply as an undesired reply considering one SSR reply, which coincides with interrogation timing t1 of one SSR interrogation, to be effective.
In the above-described SSR station, however, when one SSR reply from the aircraft 1 and the other SSR reply to the other SSR station are synchronized with each other, defruiter processing for eliminating the fruit becomes difficult and high-accuracy aircraft information is likely to become difficult to obtain.
As described above, the conventional SSR station has a problem of making defruiter processing difficult when the other SSR reply transmitted to the other SSR station from an aircraft is synchronized with the received one SSR reply.
The present invention has been developed in consideration of the above situation. One object is of the present invention is to provide an SSR station which is capable of improving in defruiter processing performance and stably acquiring aircraft information with simple construction.
Another object of the present invention is to compensate a loss of one SSR reply by separating the other SSR reply and achieve higher-precision angle measurement by both the one SSR reply and other SSR reply, thereby handling an increase in the number of aircrafts.
Still another object of the present invention is to provide an aircraft secondary surveillance network capable of monitoring an aircraft simply and easily.
According to one aspect of the present invention, there is provided an SSR station comprising interrogation transmission means for transmitting an SSR interrogation to an aircraft, reply reception means for receiving an SSR reply which is transmitted from the aircraft in response to the SSR interrogation, extraction means for processing the SSR reply received by the reply reception means, separating the SSR reply from the aircraft into one SSR reply and other SSR reply, and extracting both the one SSR reply and the other SSR reply, and means for generating aircraft information of the aircraft based on one of the one SSR reply and the other SSR reply extracted from the SSR reply from the aircraft.
The SSR station with the above configuration, using the extraction means, separates a received SSR reply into one SSR reply and the other SSR reply and extracts these relies. The SSR station generates aircraft information of an aircraft on the basis of one of the extracted replies.
Consequently even when the one SSR reply and the other SSR reply are received in a fruit state where they are synchronized with each other, the SSR station can stably acquire reliable, accurate aircraft information by reliable defruiter processing.
According to another aspect of the present invention, there is provided an aircraft secondary surveillance network comprising a plurality of SSR stations for transmitting an SSR interrogation to an aircraft, receiving an SSR reply which is transmitted from the aircraft in response to the SSR interrogation, processing the received SSR reply, separating the SSR reply from the aircraft into one SSR reply and other SSR reply, and extracting both the one SSR reply and the other SSR reply, and generating aircraft information of the aircraft based on at least one of the extracted one SSR reply and other SSR reply, and an information communication network into which the plurality of SSR stations are selectively incorporated, for communicating information between the plurality of SSR stations.
The SSR station with the foregoing configuration separates an SSR reply, which is received by itself, into one SSR reply and the other SSR reply and extracts these replies. The SSR station generates aircraft information of an aircraft based on one of the extracted one SSR reply and other SSR reply and exchange information with the other SSR station through the information communication network.
Consequently even when the one SSR reply and the other SSR reply are received in a fruit state where they are synchronized with each other, the SSR station can stably acquire reliable, accurate aircraft information by reliable defruiter processing and generate desired aircraft information upon receipt of information from another SSR station.
According to still another aspect of the present invention, there is provided an aircraft secondary surveillance network comprising an SSR station for transmitting an SSR interrogation to an aircraft, receiving an SSR reply which is transmitted from the aircraft in response to the SSR interrogation, processing the received SSR reply, separating the SSR reply from the aircraft into one SSR reply and other SSR reply, and extracting both the one SSR reply and the other SSR reply, and generating aircraft information of the aircraft based on at least one of the extracted one SSR reply and other SSR reply, a passive SSR station for intercepting an SSR reply which is issued from an aircraft in response to an SSR interrogation transmitted to the aircraft from the SSR station, and generating and monitoring aircraft information of the aircraft, and an information communication network into which the SSR station and the passive SSR station are selectively incorporated, for communicating information between the SSR station and the passive SSR station.
The plural SSR stations having the above-described configuration each separate an SSR reply, which is received by itself, into one SSR reply and the other SSR reply and extract these replies. The SSR stations generate aircraft information of an aircraft based on one of the extracted one SSR reply and other SSR reply and exchange information with the other SSR station via the information communication network. Upon receiving an SSR reply which is issued from an aircraft in response to an SSR interrogation signal transmitted from at least an SSR station to the aircraft, the plural passive SSR stations can generate and monitor aircraft information of the aircraft and exchange information with the SSR station and another passive SSR station through the information communication network.
Consequently even when the one SSR reply and the other SSR reply are received in a fruit state where they are synchronized with each other, the SSR stations can stably acquire reliable, accurate aircraft information by reliable defruiter processing and generate desired aircraft information upon receipt of information from another SSR station and a passive SSR station. The passive SSR stations can receive information from another SSR station and another passive SSR station and monitor desired aircraft information based on the received information.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.